The invention relates generally to stud welding and more particularly to a stud gun and method for using a stud gun having a stud confirmed in location for welding prior to initiating a welding sequence.
Stud welding guns are used to weld a variety of sizes of studs onto various work pieces for further attachment of additional items to the work pieces. Stud welding guns are widely used in the automotive industry to attach studs for further attachment of trim pieces on automobiles. Furthermore, stud welding guns can be used in both a manual and an automated system. Studs for use in a stud welding gun include a shaft or body often having a smooth or fastener threaded surface, and are formed of electrically conductive material. A welding current is passed through the stud which creates an arc used to fuse the stud to an electrically conductive surface (that is (i.e.), the work piece).
Common stud welding guns operate by feeding an individual stud to a collet or similar chuck device which temporarily holds the stud. The stud is then positioned approximate a work piece and a small electric current passed through the stud creates an arc between the stud and the work piece. Once the arc forms, a full welding current is applied between the stud and the work piece to generate a fusion area between the two. The stud is then rammed into the fusion area to complete the welding process. A disadvantage may result from a stud being misaligned or missing when the collet or chuck is positioned to weld. When a stud is not in position for welding, a welding arc generated between the collet and the work piece results in the collet potentially being welded to the work piece.
In either of the above situations, i.e., where the stud is missing and the process must be repeated to provide a stud in the appropriate location, and where the collet is inadvertently welded to the work piece, additional time and costs are incurred due to the delay in providing a stud or the rework required to remove the attached collet from the work piece. Stud welding gun systems are known which provide a conductivity check using a circuit path including the work piece such that the presence of a stud in position for welding is required before the arc current is generated to start the welding process. The potential for inadvertently welding the collet to the work piece is still present with these systems because the conductivity circuit is completed through the work piece, therefore requiring the stud welding gun and collet to be brought into close alignment with the work piece.
It is therefore desirable to provide a stud welding gun and stud welding gun system which reduces the potential for starting a welding process when a stud is not present and reduces the potential for welding the collet to the work piece.